The film will reportedly be based on the book "The 15:17 to Paris: The True Story of a Terrorist, a Train, and Three American Heroes," written by Jeffrey E. Stern and Anthony Sadler, Alek Skarlatos and Spencer Stone, the three passengers lauded as heroes after their quick thinking foiled a potential terrorist attack.

The three California natives, Skarlatos an Oregon National Guardsmen and Stone a U.S. Air Force Airman, were traveling through Europe on a train bound for Paris when shots rang out near the border of Belgium and France.

Alek Skarlatos competed on “Dancing with the Stars” in 2015. (Frazer Harrison/Getty Images)

The trio was able to overpower the suspect, a Moroccan national who was armed with a handgun, an automatic rifle and a knife. Their bravery was later honored internationally with several ceremonies and a flurry of press. Skarlatos embraced his fame with a stint on "Dancing With the Stars" in 2015, where he placed third.

Eastwood is fresh off the box office success of "Sully," which raked in $240 million at the box office, and is currently producing the Bradley Cooper-directed remake of "A Star is Born."